Method of and means foe



A. D. SKINNER.

METHOD or AND mums r03 HEATING PISIONS AND PREVENTING EXCESSIVE COMPRESSION m STEAM memssJ APPLICATION FILED DEC. 4. i911. RENEWED JUNE 7.1919.

1 3. 1'5, 347 Patented Sept. 9, 1919;

2 SHEETS-SHEET I.

Ill/II III 2 SHEETS-SHEET 2- A. D. SKINNER.

METHOD OF AND MEANS FOR HEATING PISTONS AND PREVENTING EXCESSIVE COMPRESSION IN STEAM ENGINES.

APPLICATION FILED DEC. 4. l9l7' RENEWED JUNE 7; I919- 3 1 5, 347 Patented Sept. 9, 1919.

UNITED STATES PATENT onn on.

' ALLAN n. SKINNER, 0F ERIE, PENNSYLVANIA.

METHOD OF AND MEANS FOR HEATING PISTONS AND PREVENTING EXCESSIVE COM- PRESSION IN STEAM-ENGINES.

Specification of Letters Patent.

Patented Sept. 9, 1919.

Application filed December 4, 1917, Serial No. 205,413. Renewed June 7, 1919. Serial No. 802,632.

T 0 all whom it may concern:

Be it known that I, ALLAN D. SKINNER, a citizen of the United States, residing at Erie, in the county of Erie and State of Pennsylvania, have invented "certain new and useful Improvements in Methods of and Means for Heating Pistons and Preventing Excessive Compression in Steam-Engines, of which the following is a specification.

This invention relates to heated pistons in steam engines of either the straight-flow type or that type of engine known as the unifiow or unidirectional-flow engine in which the steam enters at the ends of the cylinder and is exhausted through 'orts arranged at a distance therefrom axial y in the cylinder walls and ordinarily uncovered by the piston at or near the end of the working stroke.

It also applies to unifiow or unidirectional-fiow engines which have, in addition to theexhaust ports placed in the cylinder at or near the end of the Working stroke, auxiliary exhaust ports placed in the cylinder walls at the ends of the cylinder, or placed in the cylinder walls between the ends of the cylinder and the exhaust ports at or near the end of the working stroke.

W'here cylinder walls come in contact with exhaust steam, or with steam during the last stages of expansion, which iscomparatively wet steam, these walls will be colder and, in

most cases, have a film of moisture which.

much more readily absorbs the heat of the expanding steam than the walls of the cylinder if they were dry.

Steam jacketing of the cylinder walls has been attempted to free the inner walls from this moisture.

For this and other reasons, it has been found, by carefully-conducted experiments, that it is advisable to keep the cylinder walls hot and dry, especially in the case of the unidirectional-flow engine where the cylinder walls near the central exhaust ports are always colder, and therefore wetter, and,

consequently have more heat-absorption qualities, than the walls near the ends of the cylinder which have steam only at boiler pressure and temperature.

The long piston commonly used in uniflow engines entirely crosses the central exhaust ports twice on each revolution of the engine, and of course is cooled. It is further cooled on its head surfaces by the exhaust steam flowflow cylinder tends to slightly superheat this steam, so that at the end of the com- "PXGSSIOIIPGIlOd it is sometimes hotter than the boiler steam.

' In previous attempts to supply heat to a piston, it has been common to use steam coming from the main steam supply, or heat from an outside source. In this invention, however, the piston is heated by the hot compressed steam itself, and after going through the piston the steam is delivered to the main steam supply to be used in the engine as an impelling force.

The pistonitselfacts as the valve which times the introduction of the steam into the piston and its outlet into the steam supply chamber. No heat, therefore, is Wasted.

This invention has the further advantage, applied to uniflow cylinders, that it provides means to prevent the compression from greatly exceeding the initial pressure at the end of the compression stroke, which :occurs in most types of unifiow engines when the steampressure drops below that for which the clearance in the engine was de signed, or where the clearance originally was not of sufficient volume to prevent the compression from running above the pressure of the admitted steann In the accompanying drawings,-

Figure 1 is a longitudinal section of a "unifiow cylinder and hollow piston having this invention.

Figs. 2 and 3 are longitudinal sections of an improved or modified form of thesame. In thedrawings, A is the cylinder of a -uniflow"engine; B the cylinder head attached to the cylinder, and containing the inlet steam chest C in which the admission valve Dis located. The space E in the head B is in communication the inlet C, and therefore contains steam at boiler tempera ture. Fis the hollow piston of the usual length for uniflow engines, near the bottom of whose circumferential walls are located ports G and G (Fig. 1) and also H and H (Figs. 2 and 3). X are the exhaust ports. I is a groove cut in the bottom of the cylinder walls, or it may be a duct cast in the cylinder wall, or other passage, which communicates with the lineal clearance space J in the cylinder which in the position shown is filled with compressed steam. I is a similar groove at the other end of the cylinder.

It is, of course, necessary to locate the ports G, G, H and H on lines in the plston so that they do not come into communication with the central exhaust ports X in the cylinder, or any auxiliary exhaust ports, if such are used. Therefore they are placed in line with one of the bridges between said ports.

L are non-return valves, each of sufficient spring tension merely to overcome its own weight (or it might be balanced by other means) controlling ports K, K in the cylinder wall each leading to a chamber M on the outside of the cylinder and this chamber is connected, as by a pipe N, to the steam chamber E in the cylinder head B. O is a drain pipe which may be attached either to the cylinder head B or to the connectmg pipe N, as desired, the object being to rid the head of any entrained water.

In the simple form shown in Fig. 1 the piston is moved to the right to about the end of its compression stroke, and at this time the compressed steamwhich is trapped in the compression space J is forced through the passage I and port G into the hollow piston and after circulating through the same, escapes therefrom as soon as the pressure ofthe compression exceeds the pressure of the steam supply, and passes through the ports G and K, opening the valve L and passing thenoethrough the chamber M and pipe N to the chamber E in the hollow hea'd B, after which it may be used for power purposes as a part of the steam admitted through the ordinary inlet valve D. And at the end of the next stroke, if the engine is of the double acting type, the same operation takes place in a reverse direction, that is, the compressed steam enters through the port G and leaves through the port G. The ports I, K and I, K, at each end of a double acting cylinder are of course arranged to register with. the ports G and G at about the end of the compression stroke. If the engine is of thesingle acting type, port G would always be used for the admission of steam, and port G for the release of steam.

In the form shown in Figs. 9 and 3 the additional ports H and H are provided in the piston, and these respectively register with the ports K and K at each end of the stroke, in a double acting engine, the ports G and G registering with the inlets I and I only. And in this construction I provide a cross partition R in the piston, this partition extending from the bottom upwardly to about the middle of the piston. Its purpose is to prevent entrained water from rushing toward the port G' or G when it is admitting compressed steam. In this form, therefore, with the ports as shown in Fig. 2, the compressed steam enters the piston from the passage I through the port G, and circulates over the partition R and escapes with the entrained water through the ports II and K and thence to the cylinder head, the partition It serving to prevent the water of condensation being thrown by the motion of the piston toward the port G. At the end of the next stroke in a double acting engine, the steam enters through the port Gr and escapes with the water, if any, through the port H. For a single acting engine, I prefer the piston construction shown in Fig. 1. e

From the above description it will be seen that after a few strokes of the piston the interior thereof will be filled with steam of approximately the same pressure as the initial steam supplied to the interior of the hollow head B and the main inlet valves, and after this pressure is once established the trapped and compressed steam in the clearance spaces J is forced into the hollow piston, and when this increased pressure overcomes the slight tension of the valve L the compressed steam 'is forced into the hollow head and is available for power purposes, so that there is practically no loss of heat or pressure; and the time of this action is just prior to the admission of steam through the valve D for the next stroke.

The invention is not limited to an inlet valve in a hollow head, or to a cylinder having a hollow head, as the valve maybe located elsewhere and the compressed steam from the piston may be conducted to any part of the supply passage. It will be seen that the invention involves the method of utilizing the compressed steam in the clearance space of the cylinder by passing the same through the hollow piston and then into the main steam supply, and it is believed that the piston may be more'eflectually heated with this compressed steam, on account of its high temperature, than if boiler steam were used in the piston, because the compressed steam is naturally drier and it is known that at the end of the compression stroke it is hotter than the boiler steam.

- A further advantage of this invention arises from the fact that it embodies a method of and means for operating a non condensing uniflow engine without auxiliary exhaust valves and with small clearances, which has never been successfully done before, to my knowledge. That is to say in a n0n-condensing uniflow some provision must be made for preventing the compresor to provide a clearance space between the cylinder head and the piston into which space the trapped steam is compressed. The former method allows of non-condensing operation with small clearances, but with added valve gear or mechanism. The latter method necessitates largeclearance spaces 7 which are usually provided by concaving the piston or by placing clearance pockets in the heads. Both these methods of adding clearance are objectionable from aneconomical view point as clearance involves loss in economy on account. of the clearance volume itself as well as the deleterious effect of the additional superficialsurface of the metal forming the clearance space or pocket.

Other objections. are that the clearance spaces mustbe proportioned for a certain steam pressure and a certain back pressure. If the steam pressure were reduced from that for which the clearance space. was designed or should the back pressure be greater, the compression would mount above the initial pressure in the cylinder and besides causing the engine to do useless work would tend to make it noisy in operation. Such a device istherefore not flexible as well as not as economical under ordinary operating conditions as might be desired.

My invention can be applied therefore to a unifiow engine in which the clearance is a minimum even with the'engine operating non-condensing without auxiliary exhaust valves. I

By giving groove I a proper length in the cylinder Wall, so that it registersswith port G in the piston at about or' slightly before the time it is calculated that the compression will equal the initial pressure, thetrapped compressed steam between the advancing piston and the cylinder head 13 will be forced throughpiston F, heating itand afterward going to the steam supply to douseful work. 1

By this means a non-condensing uniflow can be successfully and economically operated without the use of auxiliary exhaust valves or without large clearances.

' The piston itself acts as a clearance space or pocket; but unlike the usual clearance pocket it does not allow the compressed steam from a large space, and therefore'of large volume, to be exhausted from the register with port G before the compression pressure has reached the initial pressure for which the engine is built is to prevent the compression from exceeding the initial pressure if the initial pressuieshould drop or should the back pressure be increased beyond that for which the engine was designed. Nolimitation is implied, in the claims, with respect to the particular period when the compressed steam is admitted from the cylinder to the piston. Ordinarily it will be about the end of the compression stroke.

The invention is not limited to the particular kind of engine shown 1101' to anyof the details of construction, but many modifications are possible withinthe scope of the following claims. I

I claim:

1. The method of utilizing steam in a reciprocating steam engine having a hollow piston, comprising compressing steam in the cylinder thereof, introducing such steam into the piston to heat the same, and exhausting said steam from the piston into the steam supply to the cylinder at about the time of greatest compression and thereby utilizing same in performing work.

2. The method of utilizing steam in a reciprocating steam engine having a hollow the piston during the compression stroke of the piston, and means to flow said steam from the interior of the piston to the steam supply to the cylinder.

4. In a reciprocating steam engine, the combination of a cylinder, and a hollow pistom, the cylinder and piston being provided with means to conduct compressed steam from the compression space of the cylinder into the piston during the compression stroke of the piston, said means comprising a port in the piston wall, and a passage from said space registering with said port at said time, and a passage leading from the hollow piston to the main steam inlet to the cylinder.

5. In a reciprocating engine, the combination of a cylinder, and a hollow piston, the cylinder and piston being provided with means to conduct compressed steam from the compression space of the. cylinder into the piston during the compression stroke of the piston, said means comprising a port in the piston wall, and a passage from said space registering with said port at said time, and a passage leading from the hollow piston to the main steam inlet to the cylinder, said passage having a non-return valve therein, opening toward said inlet.

6. In a reciprocating steam engine, the combination of a cylinder having a hollow head and an inlet valve therefrom into the cylinder, a hollow piston in the cylinder provided with inlet and outlet ports in the wall thereof, said cylinder having a passage from the clearance space thereof with which the inlet port registers during the latter part of the compression stroke of the piston, and also having a conduit communicating with the hollow head, with which the outlet port registers at times during the reciprocation of the piston.

7. In a reciprocating steam engine, the combination of a cylinder having a hollow head and an inlet valve therefrom into the head and an inlet valve therefrom into the cylinder, ahollow piston in the cylinder provided with inlet and outlet ports in the wall thereof, said cylinder having a passage from the clearance space thereofwith which the inlet port registers during the latter part of the compression stroke of the piston, and also having a conduit communicating with the hollow he'ad, with which the outlet port registers at times, and said piston having a partition therein between the inlet and outlet ports.

9. In a reciprocating steam engine, the combination of a cylinder having hollow heads and inlet valves therefrom into oppo site ends of the cylinder respectively, a hollow piston in the cylinder, provided with pairs of inlet and outlet ports in the wall thereof, toward opposite ends of the piston, said cylinder having at each end a passage from the clearance space thereof, with which the inlet ports respectively register at about the end of the compression strokes of the piston, and conduits opening through the cylinder wall and communicating with the hollow heads respectively and with which the outlet ports respectively register at predetermined times, and a partition in the cylinder between the respective pairs of ports.

10. The combination of a steam engine cylinder and a steam supply passage thereto, a hollow piston in the cylinder, means to conduct compressed steam from the clearance space of the cylinder into the interior of the piston, and means to return said compressed steam to the said steam passage.

11. The method of preventing excessive compression in a reciprocating steamengine, comprising admitting compressed steam from the clearance spa e of the cylinder into the interior of the piston, during the latter part of the compression stroke of the piston and returning said steam from the interior of the piston to the steam supply to the cylinder at about the time of greatest com pression.

12. The method of preventing excessive compression in a non-condensing uniflow engine, comprising admitting compressed steam from the inlet end of the cylinder into the interior of the piston at about the time during the compression stroke of the piston when the compression pressure approximates the inlet pressure and returning said steam from the interior of the piston to the steam supply to'the cylinder.

13. The method of preventing excessive compression in a reciprocating steam engine, comprising returning steam from the clearance space of the cylinder through the piston to the steam supply chamber tothe cylinder when the pressure in said clearance spaceeXceeds the-pressure in said chamber.

14. The combination with a steam engine cylinder and hollow piston,- of means for conducting steam from the clearance space of the cylinder through the piston to the steam supply to the cylinder when the pressure in said space exceeds the supply pressure to the cylinder.

In testimony whereof, I affix my signature in presence of two witnesses.

ALLAN D. SKINNER.

Witnesses ALBERT E. Ross, L. E. BARNES.

Gopies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

' Washington, D. C. 

